1. Field of the Invention
The present invention relates to thermally insulated windows for use in a curtain wall of a house or building, and more particularly to a thermally insulated window having ventilation ducts.
2. Prior Art
Thermally insulated windows composed of metallic shapes or sections, such as extruded aluminum shapes are known, in which a window sash or frame comprises interconnected interior and exterior pairs of such metallic shapes and thermally insulating connectors of synthetic resin or rubber interposed between the interior and exterior frame pieces, with panes of glass or other thermally insulating panels mounted within the window frame.
The known thermally insulated window has a drawback in that where a ventilation duct is provided in the window frame for communication between the room interior and the outside atmosphere, the thermal insulation in the vicinity of the duct becomes insufficient. This condition exists because the duct which extends between the metallic interior and exterior shapes tends to break a thermally insulated relation between the interior and exterior shapes and hence to make a thermal path therebetween. With the thermal path thus completed, a considerable amount of heat energy is transferred from the room interior to the outside air through such thermal path, thereby lowering the room air conditioning efficiency. Furthermore, during winter season when cold outside air is introduced through the duct into the heated room interior, the interior shapes become wet with condensation from room air which will cause a lowering of thermal insulating properties of the window. In order to avoid air exchange through the duct when the ventilation is not effected, there may be provided on the exterior side of the duct a pivotable valve or damper which is actuatable to open and close the duct through a power transmitting mechanism such as a link mechanism composed of a plurality of metallic links. In assembling such metallic links with the duct, care must be taken not to damage a thermal insulation between the interior side of the window and the exterior side of the window.